Cu-Cr Multilayers and Metastable Alloy Films

Abstract

A notable aspect of the copper-chromium phase diagram is the strong chemical aversion between the two elements. At room temperature, the solubility of chromium in copper is limited to .02%, while that of copper in chromium is believed to be even less [1]. The elements are even immiscible in the liquid state, exhibiting a miscibility gap which persists to an undetermined temperature. Cu-Cr alloys are of technological interest in applications ranging from electrical switches [2] to catalysis [3]. Fabrication of Cu-Cr alloys is hindered, however, by the large positive heat of mixing exhibited by the system. Cu-Cr multilayers are also of technological interest for application as soft x-ray mirrors [4]. Here the limited mutual solubility of the constituents is advantageous since interfacial mixing is reduced. In this study, we show that vapor deposition can be used to achieve complete solubility in the Cu-Cr system. On the other hand we present evidence suggesting that Cu-Cr multilayers possess sharp composition modulations with little interface mixing.